The present invention relates to a casing cover such as an exhaust casing cover in a jet engine, this cover comprising two coaxial shells arranged one inside the other and joined fixedly by radial envelopes inside which extend radial arms of the casing.
This type of cover is mounted around a jet engine bearing support and thermally protects the exhaust casing from the stream of hot gas which originates from the combustion chamber and from the turbine of the jet engine and which flows between the shells of the cover.
The cover is fastened at its downstream end to a flange of the bearing support by means of bolts and, at rest, bears at its upstream end on the casing so as to be able to expand freely under the effect of the rise in temperature during the operation of the jet engine.
However, the thermal expansion of the cover, which is greater than that of the casing, precludes the upstream end of the cover from bearing on the casing, at least during the transient phases between the idling mode and the full-power operation of the jet engine. The cover is thus mounted in cantilever fashion on the bearing support via its downstream end, and is subjected to considerable vibration stresses which may result in the appearance of fissures or cracks.
One solution to this problem would consist in modifying the geometry of the cover and/or in reinforcing it by means of stiffeners. However, this solution is not satisfactory since it is costly and leads to an increase in the mass of the cover, this being a disadvantage in the aeronautical industry.